1. Field of the Invention
The present invention relates to an inverse telephoto with correction lenses, and more particularly to a miniaturized inverse telephoto with correction lenses used in a PC CAMERA.
2. Description of the Prior Art
In recent years, with the popularity of electronic image taking equipment, such as the PC camera, and the mobile phone camera, the inverse telephoto with correction lenses has become thinner and thinner, and the sensor of a general digital camera is none other than CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). Due to advances in semiconductor manufacturing, the pixel size of sensors has been reduced continuously, and miniaturized optical lens systems for taking image have increasingly higher resolution. Therefore, the demand for image quality is increasing.
The lens assembly of a conventional PC CAMERA is usually arranged in such a manner that the front lens group is negative and the rear lens group is positive, namely, the so-called inverse telephoto structure, so as to obtain a wide field of view. And to reduce the incident angle of the light with respect to the sensor, the refractive power of the rear lens group should be improved. Usually, an ordinary rear lens group consists of two plano-convex lens elements with convex surfaces facing each other, this is the so-called RAMSDAN structure. The front lens group has negative refractive power and the rear lens group has positive refractive power, and this is an inverse telephoto. The conventional optical system here particularly refers to RAMSDAN structure of the inverse telephoto, and this structure has the following disadvantages:
The incident angle of the light with respect to the object-side surface of the second lens element of the rear lens group is too large, and as a result, the sensitivity will be increased comparatively, and the light at this position is likely to be divergent. Therefore, the system will not be stable.
The present invention mitigates and/or obviates the afore-described disadvantages.